Electrostatic spray heads are described in U.K. patent specifications Nos. 1 569 707, 2 018 601, 2 030 060 and others, and complete spray units in for example their EPA 0 118 202. Fluid supplied to the head is broken up essentially by the action of a high voltage field to form charged droplets, which are then attracted to and deposit on an earthed target such as a plant crop. The current passing, which is minute and harmless, is supplied for example by dry cells. No impellant gas or mechanical action is involved in transport of the spray.
With the growing concern over discharge of volatiles into the environment, we have sought to develop a gun using replaceable containers and allowing control of a fluid to be sprayed, at low flow rates and low pressures, such as in particular to be a replacement for the widely used aerosol sprays.